if this is all true, sounds pretty neat.. If things work out, we can get away with even more agressive cams on the street...

If it flows better at all points and works with DoD, then GM might as well start using the larger displacements on street cars for more power.. Imagine a 427 ci 550 hp "mild tune" LSx engine that still gets 30 mpg on the highway!

 

i don't see why the exhause ports are always neglected. sure there's less resistnace sucking in the air to THIS cylinder, but the next firing cylinder still does the same amount of work as before to push the exhaust out from the previous.

doesn't it seem reasonable that if you free up the intake you have to follow with the exhaust to get any real benifit? sure you suck in more air now, which means more power. but now you have more air to push out through the same opening as before which actually means MORE resistnace and more work to do than before, which should negate a good bit of that extra power gain.

does this make sense?

 

cough:346ci:cough

 

I read this article in one of the Hi-po chev mags out there and the 3rd valve is used for better emissions only. No performace gains here ladies. Unless I'm wrong and retarded

 

Nobody else answered it, but here's the short explanation for why the exhaust valves can be smaller:

Hot gases, such as those in the cylinder, have residual energy after forcing the piston down the bore, not much mass has been lost by combustion (very little), but they are occupying the same volume as they did previously, but at a much higher temperature and therefore pressure.

The difference in pressure between the exhaust manifold and the cylinder helps force the spent gases in the cylinder out, kind of like when you shake up a bottle of pop and open the top.

Because this difference in pressure is working in favor of the motor in this case, so the exhaust valve can be much smaller than the intake valve and still efficiently flow the exhaust gases out.

 

How can any mass be lost during combustion? (Or is this just taking into account blow-by?)

 

Oh sorry...that's what I get for being a smart azz I guess

And I didn't even get it right myself. Consider me

 

Someone correct me if I'm wrong...

I believe a small amout of mass is expended as it converts to kinetic energy.

 

The stuff that's converted to heat (not directly to kinetic energy) is energy that was stored in the bonds of the hydrocarbon.

 

this thread has the potential to be moved to Advanced Tech

 

Mass is not created nor destroyed. The hydrocarbons in the fuel, when ignited release energy in the form of heat increasing pressure. And thats what creates the kinetic energy.

 

Thanks, I was a recalcitrant organic chem student....I'm surprised anything stuck.

 

Well, in the end you're right....I did stretch it a bit.

 

THe 2005 Envoy and TrailBlazer Ext both will have DoD 5.3L V8s, now will these be Gen IV or GenIII V8s???

 

A small amount of mass (unmeasureable in terms of standard chemistry practices) is converted to energy during combustion.

If you look at things in an Einsteinian way, instead of Newtonian, it works.

"Mass is not created nor destroyed."

Depends on what you call "destroyed" or "created" as mass and energy are interchangeable.


In fusion or fission, a MUCH larger amount of mass is expended... i.e. turned into energy.